FR2467473A1 - CURRENT TRANSFORMER FOR HIGH VOLTAGE INSTALLATION - Google Patents

Abstract

The invention relates to a current transformer for high voltage installation comprising a primary winding, a secondary winding and a magnetic circuit, said primary winding comprising a primary turn suspended from two coaxial conductors in an insulating enclosure containing a dielectric body. The transformer is characterized in that the secondary winding 28 and the magnetic circuit 27 are arranged around the primary turn 6 outside the enclosure. The invention applies in particular to very high voltage installations. (CF DRAWING IN BOPI)

Description

The invention relates to a current transformer for

high voltage installation.

  Usually, the primary circuit is isolated from the earth for the permanent operating voltage and for the test voltages specified by the regulations, the secondary circuit is isolated from the primary circuit, and one of its terminals is usually earthed. . The magnetic circuit is either grounded or put at the potential of the next high voltage that the insulation between

  Primary and secondary education is relevant to the primary or secondary school (s).

  In the case of magnetic ground circuit, it and the secondary circuit are embedded in a solid insulating material, or housed in a shell itself to the ground and filled with a liquid or gaseous insulating fluid. These envelopes are bulky to contain the magnetic circuits and require, for the exit of the terminals of the secondary ones, difficult crossings to difficult to

  get and expensive. Magnetic circuits are inaccessible.

  As for the solid insulators used between live parts and earth, they are dielectrically very constrained and may be subject to aging. On the other hand, current transformers for high-voltage installations generally have a rated current

  high and, therefore, the primary circuit has a single sphere.

  Under these conditions, even during a short circuit or a lightning strike, the voltage across the primary circuit is always

very weak.

  It is therefore interesting to avoid the presence of organic insulation between the primary conductor and the mass while-the presence of organic insulation between various elements of the primary conductor does not present any real inconvenience. The object of the invention is a current transformer in which the arrangement of the constituent elements allows simplified insulation, better accessibility and consequently

an advantageous implementation.

  The subject of the invention is a current transformer for a high-voltage installation comprising a primary winding, a secondary winding and a magnetic circuit, said primary winding comprising a primary winding suspended from two coaxial conductors in an insulating enclosure containing a body dielectric, characterized in that the secondary winding and the magnetic circuit

  are arranged around the primary turn outside the enclosure.

  According to one characteristic, the primary turn is disposed in an annular tank constituted by several metal elements and the magnetic circuit and the secondary winding are arranged around a carrier element separated from one of the adjacent elements by a insulating joint, the electrical continuity of the tank being provided by an electrical connection connecting around the magnetic circuit and the secondary winding said element adjacent to the end of said carrier element opposite the other adjacent element. According to another characteristic, the dielectric body

  in the insulating enclosure is constituted by a gas. -

  The outer coaxial tube may be constituted by a tube of high mechanical rigidity and the outer coaxial tube may comprise

at least one steel part.

  According to one embodiment, the insulating enclosure comprises a set of insulators of decreasing diameter from bottom to top,

  coaxial conductors resting on the upper end of the isolate

superior.

  The primary turn has on its ends a conical sleeve whose top is provided with a cylindrical connection, one of these connections being connected to a cylindrical connector disposed at the end of a conical sleeve of the outer coaxial tube and the another connector being connected to the central coaxial conductor through the cylindrical connector of the outer coaxial tube. This primary turn can be toric. A visit door is arranged on the metal tank containing the primary turn to the right of its connection with the coaxial conductors. The features and advantages of the invention will become apparent

  in the description given below, with regard to an embodiment

illustrated in the figures.

  FIG. 1 is a diagrammatic view in axial section of a transfor-

according to the invention.

  FIG. 2 is a detail view showing the junction

  between the coaxial conductors with the primary coil.

  In the figures, 1 has designated the input terminal of the primary circuit of an intensity transformer connected by a central and vertical conductor 2 to the end of an annular primary turn 6.

  The other end of the primary turn 6 is connected by a conductive tube

  external coaxial wire 3 to the output terminal 4 of the primary circuit.

  Terminal 1 and the central conductor 2 are isolated from terminal 4

  and the coaxial tube 3 by an insulating ring 5.

  The primary circuit is disposed inside a sealed enclosure filled with dielectric gas such as sulfur hexafluoride. The sealed enclosure comprises a vertical upper part constituted by a stack of tubular insulators such as 9 and 17, which are staggered in diameter, allow assemblies to be made.

  modular that can be combined according to the insulation voltage.

  Collars 8, 18, 19 and 20 are sealed on the ends of the insulators. The collars of different diameter such as 18 and 19 are fixed on an intermediate plate 21. Guard rings such as 22 connected to the plate 21 and arranged opposite provide

  the distribution of the electric field.

  The coaxial conductors 2 and 3 are suspended vertically in the axis of the insulators 9 and 17 through an end plate 7

  attached to the top collar of the insulator 9.

  The lower part of the sealed enclosure is constituted by an annular metal tank 16 in the inner axis of which is disposed the primary coil 6. The metal vessel is made using several sections 33, 34, 35 and 36. The upper section 33 has an upper opening connected through a plate 32 to the lower collar 20 of the lower insulator 17 and an opening

  lower closed by a door 26.

  The ends of the upper section 33 are connected to the lateral sections 34 and 35, which are themselves connected to the horizontal lower section 36. However, an insulating joint 24 is interposed between the metal sections 34 and 36. The sealing between the various constituent elements of the sealed enclosure is conventionally provided by seals and the lower section 36 is provided with a filler plug 25 of the dielectric gas, and a device

pressure control.

  The primary turn 6, which is tubular, has at its ends frustoconical sleeves 41 and 42 provided on their top with cylindrical connectors 43 and 44. The coaxial tube 3 comprises at its lower end a frustoconical sleeve 10 provided at its apex with a Ring

  cylindrical connection piece 11 connected on its periphery to the connection 44.

  The lower end of the central conductor 2 comprises, inside the ring 11, a cylindrical shoulder 12 isolated from the ring 11

by an insulating tube 14.

  The ring 11 and the insulating tube 14 have on their lateral face opposite the connection 44 a lateral opening in which is disposed an insulating tube 15 through which the connector 43 carries at the end a connection pad 13 screwed to the end of

the shoulder 12.

  The outer coaxial tube 3 can be very rigid and constituted, for example, by a rather thick aluminum alloy tube or even

  because the coaxial arrangement of the drivers cancels

  the resulting magnetic field. The secondary circuit of the transformation

  intensity meter is disposed in the open air around the lower metal section 36. It thus comprises a magnetic circuit 27 around which is wound the secondary winding 28. Equipotential conductive links such as 29 arranged around the secondary circuit connect the end of the lateral section 34 next to the insulating joint 24

  at the end of the lower section 36 opposite the insulating joint 24.

  Since the voltage between the terminals 1 and 2 of the primary winding is always very small compared to the voltage between the primary conductor and the ground, the insulator 5 and the tubes 14 and 15 require only

  dielectric and it is possible to use these parts

organic insulators.

  Fixing the current transformer in the station can be carried out using a chassis 31 provided with feet 30 fixed to the plate 32 on which is mounted the lower collar 20 of the insulating envelope. The tank 16 is suspended from the frame 31, which avoids the - 5 deformations of the tank, and this frame supports the insulating envelope

  at the top of which is suspended the whole of the hoist

primary element.

  Such a current transformer can be used as a disconnector element support isolator. The door 26 allows, during assembly, to introduce a removable tool of appropriate shape. The latter, by using as a geometric reference the bearing surface of the door 26, allows the height and rotation adjustment around the vertical plane of symmetry of the primary circuit, in order to ensure the best possible centering of the live parts. in the tank to the ground. After positioning and immobilization of the primary circuit, the tooling is removed and

close the door 26.

  The insulation between the primary winding 3, 6 and the tank 16 to the ground being only achieved by the insulating gas, the only line of leakage between live parts and mass that exists along

  ceramic insulators 9 and 17, has a very long length.

  There is no organic insulation supporting the high voltage applied between the primary and the ground. The tank 16 is provided with a valve and / or a membrane limiting any overpressure

  due to an internal arc for example, thus avoiding any risk of explo-

  if we. The current transformer according to the invention has many advantages: - The use of a primary coil connected to two coaxial conductors, suspended in a chamber filled with gas and in contact with solid parts only at the point of suspension makes it possible to apply the high voltage between the primary winding and the mass only through a gas and along a very long line of leakage along

a ceramic insulator.

  - No organic insulation is subject to the stress of

very high voltage.

  The use of secondary windings arranged outside the enclosure containing the insulating gas makes it possible: to minimize the volume of gas, since in all points the thickness of the gas corresponds to the dielectric strength between 6 - surfaces with large radius of curvature. Similarly, the junction of the coaxial

  and the primary coil avoids any discontinuity causing an increase

localization of the electric field.

  it is much easier to assemble the secondary windings and any modifications to them. to obtain, thanks to an external electrical connection to the magnetic and secondary circuits, the electrical continuity of the tank without

  alteration of the properties of the magnetic circuit.

  - The centering of the coaxial conductors and the primary turn can be achieved easily through the use of a visit door. - The use of cylindrical insulators, staggered in diameter and constituting modular assemblies that can be combined according to the insulation voltage, reduces manufacturers' manufacturing costs.

  realizing devices of several nominal voltages.

  - The addition of a disconnector to the current transformer

  allows the common use of the same insulators supports.

  - The mounting of such a current transformer instead

  an isolating support on disconnector saves an insulating support.

  It is obvious that the invention is not limited to the embodiment which has just been described and shown and which has been given only as an example; in particular, it is possible, without departing from the scope of the invention, to modify certain provisions or to replace certain means by equivalent means, or else to replace certain elements by others capable of providing the same technical function.

  or an equivalent technical function.

  In particular, the annular turn 6 can be a torus that is practically insensitive to electrodynamic forces (circular turn), thus eliminating the stresses and deformations of the turn during the

  passage of short circuit current.

2467473:

-7-

Claims (8)

  1 / Current transformer for a high-voltage installation comprising a primary winding, a secondary winding and a magnetic circuit, said primary winding comprising a primary coil suspended from two coaxial conductors in an insulating enclosure containing a dielectric body, characterized in that secondary winding (28) and the magnetic circuit (27) are arranged around   the primary turn (6) outside the enclosure.   2 / transformer according to claim 1, characterized in that   the primary turn (6) is arranged in an annular tank (16) constituting   with the aid of several metal elements (33, 34, 35, 36) and that the magnetic circuit (27) and the secondary winding (28) are arranged around a carrier element (36) separated from one (33) adjacent elements by an insulating joint (24) the electrical continuity of the tank being provided by an electrical connection (29) connecting around the magnetic circuit and the secondary winding said element adjacent to the end of said carrier member; look of the other adjacent element.   3 / transformer according to one of claims 1 and 2, characterized   in that the dielectric body contained in the insulating enclosure is constituted by a gas.   4 / transformer according to one of claims 1 to 3, characterized   in that the insulating enclosure comprises a set of insulators (17, 9) of decreasing diameter from bottom to top, the coaxial conductors   (2, 3) resting on the upper end of the upper insulator.   Transformer according to one of Claims 1 to 4, characterized   in that the outer coaxial tube (3) consists of a tube of high mechanical rigidity.   6 / Transformer according to claim 5, characterized in that   the outer coaxial tube (3) has at least one steel part.   7 / Transformer according to one of claims 1 to 6, characterized   in that the primary turn has on its ends a conical sleeve (41, 42) whose apex is provided with a cylindrical connection (43, 44), one of these connections being connected to a cylindrical connection (11).   disposed at the end of a conical sleeve (10) of the outer coaxial tube   2467473 (3) and the other connection being connected to the central coaxial conductor   (2) through the cylindrical connector of the outer coaxial tube.   8 / transformer according to claim 2, characterized in that a visit door (26) is disposed on the metal vessel (16) containing the primary coil (6) to the right of its connection with the conductors coaxial (23).   9 / Transformer according to one of claims 1 to 9, characterized   in that the primary worst (6) can be toric.